Water O–H
Stretching Raman Signature for Strong
Acid Monitoring via Multivariate Analysis
- Publication date
- Publisher
Abstract
A distinct need exists for real time
information on an acid concentration
of industrial aqueous streams. Acid strength affects efficiency and
selectivity of many separation processes, including nuclear fuel reprocessing.
Despite the seeming simplicity
of the problem, no practical solution has been offered yet, particularly
for the large-scale schemes involving toxic streams such as highly
radioactive nuclear wastes. The classic potentiometric technique is
not amiable for online measurements due to the requirements of frequent
calibration/maintenance and poor long-term stability in aggressive
chemical and radiation environments. Therefore, an alternative analytical
method is needed. In this work, the potential of using Raman spectroscopic
measurements for online monitoring of strong acid concentration in
solutions relevant to dissolved used nuclear fuel was investigated.
The Raman water signature was monitored for solution systems containing
nitric and hydrochloric acids and their sodium salts of systematically
varied composition, ionic strength, and temperature. The trivalent
neodymium ion simulated the presence of multivalent f metals. The
Gaussian deconvolution analysis was used to interpret observed effects
of the solution nature on the Raman water O–H stretching spectrum.
The generated Raman spectroscopic database was used to develop predictive
multivariate regression models for the quantification of the acid
and other solution components, as well as selected physicochemical
properties. This method was validated using independent experiments
conducted in a flow solvent extraction system